The present invention relates to rectification of ethanol and production of fuel grade ethanol from beer using an energy efficient chromatographic rectification process.
The production of fuel grade ethanol by fermentation has become a large source of transportation fuel in the United States and in particular, in the corn belt states of Indiana, Illinois, Iowa, Minnesota and the Dakotas. Ethanol is produced typically from corn, but other substrates are available by the yeast fermentation of sugars to produce a beer containing typically from 10 to 15% ethanol. The ethanol is recovered from the beer by a distillation process that is energy intensive. Fuel grade ethanol is recovered from beer in a two-part process. In the first part, called the beer stripper, beer is fed to the top of a column containing multiple trays, 15 to 25 being typical. Energy is fed to the beer column via a reboiler at the bottom of the beer stripper when steam is formed and passes upward through the beer stripper as beer flows down across the trays. Because the ethanol is more volatile than water, the rising steam exchanges energy causing the ethanol to vaporize and the steam to condense. Continuing in this manner to the bottom of the beer stripper, the ethanol content at the bottom is reduced to a low level (0.1%) or less. The ethanol rich vapor rises through the column and exits the beer stripper to the rectifier.
In the rectifier the vapor from the stripper column is enriched further. The vapor from the stripper section enters the bottom of the rectifier and rises in counter current flow to a stream of high concentration ethanol introduced at the top of the rectifier column. The highly enriched vapor then passes out the top of the rectifier for recovery.